Method for processing hot strip coils

Abstract

The invention relates to a method for processing hot-rolled coils, in particular coils made of hot-rolled steel, comprising the steps (1.) of placing a round, wound-up hot-rolled coil on a base, preferably in a coil tray or pallet, (2.) of forming the coil from a round shape into a non-round shape by applying a forming force to two opposite sides of the coil, (3.) of forming the formed non-round coil into a round shape under the influence of the dead weight of the hot-rolled coil.

Description

1. Field of the invention

[0001] The invention relates to a method for processing hot-rolled coils, in particular coils made of hot-rolled steel, which tend to collapse after winding until a temperature threshold is reached due to their own weight and consequently lose their round winding shape. 2. State of the art

[0002] Hot-rolled coils, especially those made of steel strip, are often not subjected to accelerated cooling after winding to avoid undesirable changes in the microstructure. Instead, in many applications, it is common and necessary to ensure slow cooling to room temperature. This slow cooling process establishes the desired microstructure with the intended microstructural constituents, grain sizes, and ultimately, material properties.

[0003] After winding, hot-rolled coils are typically unwound from the mandrel and rest on a suitable support, such as a coil stand or pallet, without being supported in the coil eye. Due to the coil's own weight, usually between 10 and 55 tons, coil eye collapse is frequently observed, resulting in an overall irregular shape of the coil. Winding above the transformation temperature causes a change in the strip's volume during cooling, which also leads to loose windings within the coil. This effect is a primary cause of coil deformation. However, this is undesirable for further processing, transport, and ensuring homogeneity of material properties along the entire length of the wound strip.Only after a certain temperature threshold is crossed does the strip wound into a coil typically exhibit a strength sufficient to reliably prevent undesirable deformation of the coil from its non-round shape, up to and including a possible collapse of the coil eye.

[0004] The phenomenon of coil collapse is well known, and various approaches exist in the prior art to address this problem or to continue operating coils that have already collapsed. Examples include EP 3 774 105 B1, JP H09-24 419 A, and WO 2024 / 036 988 A1. Approaches to preventing coil collapse involve, for instance, a virtually permanent rotation of the coil so that the force of gravity acts uniformly across its entire circumference. Similarly, approaches are known that involve allowing the coil to deform over a predefined period, then rotating it 90°, and finally waiting for it to deform back into its original round shape.All these prior art approaches only reactively address the problem of coil collapse or at least undesirable coil deformation due to the effects of gravity and the coil's own weight, which means that cycle times within a production plant cannot be optimally adjusted. This is where the invention comes in. 3. Object of the invention

[0005] It was an object of the invention to overcome the problems known from the prior art and to proceed proactively, rather than reactively, in order to optimize the cycle times of a production plant. This object is achieved according to the invention by a method comprising the features of claim 1. Advantageous embodiments of the invention are set forth in particular in the dependent claims. 4. Summary of the invention

[0006] According to the invention, a method for processing hot-rolled coils, in particular coils made of hot-rolled steel, is provided, comprising the steps of placing a round, wound-up hot-rolled coil on a base, preferably a coil tray or pallet, forming the coil from a round shape into a non-round shape by applying a forming force to two opposite sides of the coil, and subsequently deforming the formed non-round coil into a round shape under the influence of the dead weight of the hot-rolled coil.

[0007] The invention is applicable to all types of hot-rolled strips that tend to lose their original round shape due to their own weight, at least above a material-dependent temperature threshold. This applies in particular to steel strips, but also to non-ferrous metals such as copper or its alloys.

[0008] Coils are typically wound in a reeling device such that the longitudinal orientation of the coil eye, and thus the axis of rotation of the coil, is horizontally aligned. The hot-rolled strip, usually with a width of 0.8 to 2.6 m, is then wound into a coil weighing 10 to 55 tons and, after winding, rests on the outer winding of the strip. The coil is typically stored and transported in this position and orientation. The invention relates specifically, though not exclusively, to hot-rolled strip coils held and, if necessary, transported in this typical position and orientation.

[0009] Hot-rolled strip production typically involves immediately winding the strip onto a reel to form a coil. This allows for the further transport of the hot-rolled strip, which, depending on its thickness, can exceed 200 meters in length, as otherwise it could no longer be stored and transported without being cut to length. Furthermore, tightly winding the hot-rolled strip into coils significantly reduces the cooling rate, which is desirable or even necessary depending on the desired properties of the cooled strip and the associated requirements for its structure. In particular, winding the strip into coils effectively prevents excessive cooling using simple means.

[0010] The invention thus relates to a process in which, in a first step, the coil is deliberately transformed from a round original shape into a non-round preform, which is ultimately undesirable for the final product, and is then reshaped under the influence of gravity and the coil's own weight, preferably exactly back into its original round shape immediately after leaving the reel. The invention therefore provides a proactive approach, whereby the aforementioned steps of the process can be repeated as necessary, at least until the hot-rolled coil reaches a temperature at which undesirable coil deformation or even coil collapse no longer occurs.

[0011] In a preferred embodiment of the method according to the invention, the steps of forming the coil from a round shape into a non-round shape by applying a forming force to two opposite sides of the coil, and of deforming the formed non-round coil into a round shape under the influence of the self-weight of the hot strip wound into a coil, are repeated several times until the coil, upon cooling, exhibits sufficient inherent stiffness at which no deformation of the coil occurs under the influence of its own weight. Such sufficient inherent stiffness is temperature- and material-dependent; those skilled in the art know the material-dependent temperature thresholds, possibly also taking into account a limit value deemed acceptable for any residual deformation.This consideration disregards the elastic deformation behavior of the coil and the material; the focus is regularly on plastic deformation, to which the coil should ultimately no longer be subject due to its own weight.

[0012] According to a further preferred embodiment of the invention, the coil is transported between the aforementioned steps to another support or by means of a mobile support itself. This could be, for example, coil transport trolleys, coil pallet trucks, optionally self-propelled coil pallets, or the like. The method according to the invention is not limited to the type or location of the support; rather, it focuses on the fact that a coil is deliberately formed in a specific orientation and can then be reshaped back into its original shape under the influence of gravity and the coil's own weight. The transport of the formed coil can preferably take place while it is still in its non-circular form, and the reshaping back into its original round shape can be carried out at another location, for example, in a warehouse.

[0013] In a preferred embodiment of the invention, the inventive method is carried out directly after the hot strip exits a hot rolling mill and is wound into a hot strip coil. This allows, on the one hand, the direct use of the hot strip without further preheating and, on the other hand, the fastest possible proactive action after coiling, in particular for optimizing the cycle times desired in the plant.

[0014] It is particularly preferred if the forming force for transforming the round coil into a non-round shape is applied to the coil from the outside, preferably also by applying the forming force symmetrically to the coil. This creates a method that allows for simple handling with readily accessible and easily controllable means.

[0015] As mentioned above, it is preferred that the coil rests on the base with a free coil eye, preferably without the use of a mandrel or support in the coil eye.

[0016] The coil is formed after being placed on the support such that, after forming, it has a vertically oriented diameter that is larger than a horizontally oriented diameter, preferably an upright oval shape. This allows the coil, after proactive forming into a non-circular shape, preferably an oval shape, to undergo a subsequent deformation directly and immediately in the direction of gravity due to its own weight, without the need for further rotation, which, according to the invention, returns the coil to its original shape.

[0017] In an alternative and equally preferred embodiment of the invention, after the active forming step, the coil is rotated into a non-circular shape such that its vertically oriented diameter is larger than its horizontally oriented diameter, preferably resulting in an upright oval shape. Optimally, in both of the aforementioned alternative and preferred embodiments, the method according to the invention is implemented such that the vertically oriented diameter of the formed coil is the maximum diameter of the coil and the horizontally oriented diameter of the pre-formed coil is the minimum diameter. This enables uniform re-forming of the pre-formed coil into its original shape under the influence of gravity without the need for readjustment of its position and orientation on the support.

[0018] In a further embodiment of the invention, it is preferred that the coil eye has a horizontally arranged longitudinal extension throughout the entire process, thereby enabling uniform reshaping of the entire coil under the influence of gravity without the need to reposition the coil.

[0019] The invention can preferably be implemented on a system for carrying out a method according to the invention, wherein the system is set up and designed to execute the method according to the invention. This may also include the automated control of the method with regard to the forming forces used, the forming forces acting upon the coil, the forming speeds, and the times for the reshaping of the pre-formed coil, preferably stored in the control unit.

[0020] The system comprises a support for setting down a hot-rolled coil, preferably a coil made of hot-rolled steel strip, and a device for applying a forming force to two opposite sides of the coil. This ensures that the forming force can be applied symmetrically to the coil and that readjustment of the coil's position and orientation after it has been formed into a non-circular shape is no longer necessary.

[0021] In this context, it is preferred if the device for applying the forming force has two forming cylinders arranged on each side of the base, which are designed and arranged so that they can be moved relative to each other.

[0022] It is particularly advantageous if these forming cylinders can be hydraulically actuated. This creates a device that can precisely control both the forming force and the degree of forming itself using readily available and easily manageable means.

[0023] It is also preferred if the forming cylinders have at least two support rollers at their opposite ends, which are preferably designed and arranged in such a way that they prevent the outer winding of the coil from springing up and at the same time prevent damage to the surface of the strip wound into the coil.

[0024] In this context, it is also preferred if the support rollers on each side of the coil are connected to the respective forming cylinder via a common base and are also pivotably connected. This allows the support rollers to self-align to different coil diameters and simultaneously ensures a symmetrical application of the forming forces to the coil via the two forming cylinders. 5. Description of the figures

[0025] The invention is explained in more detail below with reference to two figures, in which Fig. 1 shows a cross-sectional view of a system for carrying out the method according to the invention, and the Fig. Figures 2a to 2c show a sequence of the process steps according to the inventive method. 6. Detailed description of the figures

[0026] Fig. Figure 1 shows a cross-sectional view of a system 1 designed and set up for processing hot-rolled coils. The system 1 has a coil support 2 on which a coil 3 of hot-rolled strip can be placed. The coil 3 rests on the coil support 2 such that its center of rotation, in particular the longitudinal axis of the coil 3, is centered within the system 1. Forming cylinders 4a, 4b are arranged on both sides of the coil 3, which can at least indirectly impart movement to the support rollers 5a, b and 5c, d on the outside of the coil 3. The forming cylinders 4a, 4b act on levers (not shown) which are connected at their lower end to a rotary bearing 6a, 6b and at their upper end to a base 7a, 7b for the support rollers 5a, b and 5c, d.When the forming cylinders 4a, 4b are moved towards each other, the levers (not shown) can be pivoted around the rotary bearings 6a, 6b so that the base 7a and the base 7b are moved towards the outer circumference of the coil 3. The support rollers 5a, b and 5c, d thus perform a support function when simply resting against the circumference of the coil 3 and, if necessary, prevent the outer winding of the coil 3 from springing back. On the other hand, the support rollers 5a, b and 5c, d can also, under the influence of the forming cylinders 4a, 4b, effect a forming of the coil 3 by... Fig. The round shape of the coil 3 shown in Figure 1 is modified. The support rollers 5a, b and 5c, d are arranged within the system 1 such that they engage the outer circumference of the coil 3 above and below its horizontal plane of symmetry and are rotatably connected to the upper end of the levers (not shown) in such a way that they automatically adjust to the circumference of the coil 3, regardless of its diameter. The arrangement of forming cylinders 4a, 4b on the levers (not shown) and the support rollers 5a, b and 5c, d is symmetrical to the coil 3 to enable uniform forming of the coil 3 under the influence of the forming cylinders 4a, 4b and the support rollers 5a, b and 5c, d. The base 7a, 7b is connected to the lever (not shown) such that its pivot point is located below the horizontal plane of symmetry of the coil.The levers (not shown) can be adjusted in length to allow the system 1 to be adapted to the height of the coil 3. This enables a consistently uniform application of the forming force to the coil 3, the lower edge of which remains at a stationary height on the coil support 2 and whose center point, like the upper edge of the coil 3, moves upwards during the forming process.

[0027] Fig. 2 shows in the sequence of Fig. 2a, Fig. Figures 2b and 2c describe the inventive method, beginning with the still round coil 3 made of hot-rolled strip, which was placed on the coiling tray 2 immediately after being wound up. The coil eye 8 is exposed, meaning that no support function is provided for the coil 3 and the coil 3 is entirely subject to the influence of gravity. Fig. Figure 2b shows the state of coil 3 after the step of forming it from a round shape to a non-round shape by applying a forming force to two opposite sides of the coil. It is clearly visible that the coil 3 was formed by the (not shown) machine in such a way that its diameter in the vertical direction is larger than its diameter in the horizontal direction. The oval shape of coil 3 shown here is symmetrically aligned with respect to the vertical central axis through coil 3 or the coil support 2. Fig. 2c Finally, the coil 3 is shown in a state after step 3 of the deformation (so-called "sagging") of the formed non-round coil 3 into a round shape under the influence of the self-weight of the hot strip wound into a coil 3. The coil 3 has, starting with the oval shape of Fig. 2b, under the influence of gravity and the self-weight of the coil 3, and due to the fact that the hot-rolled strip does not have sufficient inherent stiffness and strength to retain its own weight while maintaining its shape, deformation from the oval shape shown in Fig. 2b, back into a round shape, shown in Fig. 2c, completed. Provided it is in the condition according to Fig. 2c If the inherent stiffness and strength of the coil 3 are considered sufficient, the coil 3 can remain in place or be transported further without being reshaped. Preferably, however, the coil 3 can also be reshaped in the state according to Fig. 2b transported after the forming process has been completed and before the re-forming process ("sagging") is finished. Reference symbol list 1 Annex 2 Bundling 3 Coil 4a, 4b forming cylinders 5a,b, 5c,d Stützrollen 7a, 7b Basis 8 Coilauge

Claims

[1] Method for processing hot-rolled coils (3), in particular coils (3) made of hot-rolled steel strip, comprising the steps (1.) placing a round, wound-up hot-rolled coil (3) on a support, preferably a coil tray (2) or pallet, (2.) forming the coil (3) from a round shape into a non-round shape by applying a forming force to two opposite sides of the coil (3), and (3.) subsequently deforming the formed non-round coil (3) into a round shape under the influence of the self-weight of the hot-rolled strip wound into a coil (3). [2] Method according to claim 1, characterized by that steps (2.) and (3.) are repeated until the coil (3) has sufficient inherent stiffness due to cooling, at which no deformation of the coil (3) occurs under the influence of its own weight. [3] Method according to any one of the preceding claims, characterized by, that between steps (2.) and (3.) the coil (3) is transported to another support or by means of the first support. [4] Method according to any one of the preceding claims, characterized by , that the process is carried out directly after the hot strip exits a hot rolling mill and is wound into a hot strip coil (3). [5] Method according to any one of the preceding claims, characterized by , that the forming force for forming the round coil (3) into a non-round shape is applied to the coil (3) from the outside. [6] Method according to any one of the preceding claims, characterized by , that the forming force is applied symmetrically to the coil (3). [7] Method according to any of the preceding claims, characterized by that the coil (3) rests on the base with a free coil eye (8), preferably without an insert or support. [8] Method according to any of the preceding claims, characterized by, that the coil (3) after step (2.) has a vertically oriented diameter which is larger than its horizontally oriented diameter, preferably the coil (3) has an upright oval shape. [9] Method according to any one of claims 1 to 7, characterized by , that the coil (3) is rotated before carrying out step (3.) so that it has a vertically oriented diameter which is larger than its horizontally oriented diameter, preferably the coil (3) has an upright oval shape. [10] Method according to any one of the preceding claims, characterized by , that the coil eye (8) has a horizontally arranged longitudinal extent throughout the entire process. [11] Method according to any of the preceding claims, characterized by , that step (3.) is carried out without external influence or a device (4) applying a forming force.

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